Magnesium1-3, zinc4-6 and some other impurities (substituting mainly for the lithium sites) drastically change optical properties of LiNbO3. In particular the value of optical damage (photorefraction) in LiNbO3:Me (Me = Mg,Zn,…) is sharply reduced compared with undoped LiNbO32-6. Similarly Me impurities tend to supress so-called "dark trace” effect4-6 (that means stable darkening under intensive visible laser radiation).
{"title":"Optical Damage Resistant Impurities in Lithium Niobate","authors":"T. Volk, N. Rubinina, S. Stizza","doi":"10.1364/JOSAB.11.001681","DOIUrl":"https://doi.org/10.1364/JOSAB.11.001681","url":null,"abstract":"Magnesium1-3, zinc4-6 and some other impurities (substituting mainly for the lithium sites) drastically change optical properties of LiNbO3. In particular the value of optical damage (photorefraction) in LiNbO3:Me (Me = Mg,Zn,…) is sharply reduced compared with undoped LiNbO32-6. Similarly Me impurities tend to supress so-called \"dark trace” effect4-6 (that means stable darkening under intensive visible laser radiation).","PeriodicalId":355924,"journal":{"name":"Photorefractive Materials, Effects, and Devices","volume":"116 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1994-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124123166","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In paper1 the effective recording of hologram gratings in photorefractive cryctals by short light pulses was studied experimentally. The self-diffracthion theory of light pulses for the time of Maxwell’s relaxation τm which was negligible compared with the pulse duration τu was investigated by Kuchtarev and Semenetz2. Here we did not take into account the influence of piezoelectric and photoelastic effects that might have a strong influence on hologram recording and restoration3. The results of the analysis of hologram grating pulse recording in photorefractive crystals accounting for piesoelectric and photoelastic effects for τu«τm.
{"title":"Influence of Piezoelectric and Photoelastic Effects on Pulse Holotgram Recording in Photorefractive Crystals","authors":"R. Litvinov, S. Shandarov","doi":"10.1364/JOSAB.11.001204","DOIUrl":"https://doi.org/10.1364/JOSAB.11.001204","url":null,"abstract":"In paper1 the effective recording of hologram gratings in photorefractive cryctals by short light pulses was studied experimentally. The self-diffracthion theory of light pulses for the time of Maxwell’s relaxation τm which was negligible compared with the pulse duration τu was investigated by Kuchtarev and Semenetz2. Here we did not take into account the influence of piezoelectric and photoelastic effects that might have a strong influence on hologram recording and restoration3. The results of the analysis of hologram grating pulse recording in photorefractive crystals accounting for piesoelectric and photoelastic effects for τu«τm.","PeriodicalId":355924,"journal":{"name":"Photorefractive Materials, Effects, and Devices","volume":"23 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1994-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114211495","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A. Ennouri, M. Tapiero, J. Vola, J. Zielinger, J. Moisan, J. Launay
Sillenites are potentially a promising class of photorefractive materials for specific applications provided that crystals, insuring the corresponding optimal and reproducible operating characteristics, could be prepared. The first step in this direction is to measure and to check the reproducibility of the involved properties of the as-grown material obtained by the usual Czochralski technique which in fact works under relatively well defined conditions. In this respect, the determination of the mobility of photocarriers (electrons in BGO) and the knowledge of the mechanism of charge transport are of fundamental importance.
{"title":"Determination of the Mobility and Transport Properties of Photocarriers in BGO by the Time-of-Flight Technique","authors":"A. Ennouri, M. Tapiero, J. Vola, J. Zielinger, J. Moisan, J. Launay","doi":"10.1063/1.354752","DOIUrl":"https://doi.org/10.1063/1.354752","url":null,"abstract":"Sillenites are potentially a promising class of photorefractive materials for specific applications provided that crystals, insuring the corresponding optimal and reproducible operating characteristics, could be prepared. The first step in this direction is to measure and to check the reproducibility of the involved properties of the as-grown material obtained by the usual Czochralski technique which in fact works under relatively well defined conditions. In this respect, the determination of the mobility of photocarriers (electrons in BGO) and the knowledge of the mechanism of charge transport are of fundamental importance.","PeriodicalId":355924,"journal":{"name":"Photorefractive Materials, Effects, and Devices","volume":"26 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1993-08-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127891675","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Generation of spatial subharmonics is considered as a consequence of convective instability in parametric nonlinear mixing of tree copropagating coherent waves of the same frequency: two incident pump waves and the scattered wave, propagating at the bisector of pump waves.
{"title":"Spatial Subharmonic Generation in BaTiO3","authors":"A. Novikov, S. Odoulov, R. Jungen, T. Tschudi","doi":"10.1364/JOSAB.9.001654","DOIUrl":"https://doi.org/10.1364/JOSAB.9.001654","url":null,"abstract":"Generation of spatial subharmonics is considered as a consequence of convective instability in parametric nonlinear mixing of tree copropagating coherent waves of the same frequency: two incident pump waves and the scattered wave, propagating at the bisector of pump waves.","PeriodicalId":355924,"journal":{"name":"Photorefractive Materials, Effects, and Devices","volume":"55 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1992-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134184777","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A new configuration of an all-optical, nonlinear holographic associative memory [1] is investigated. A multistable, content-addressable cavity is used, that performs image comparison, discrimination and read-out in one step. The required nonlinear processes are obtained by using a combination of a photorefractive KNbO3 crystal and a nematic liquid crystal (NLC) in a feedback configuration with several beams.
{"title":"All-Optical Associative Memory based on a Nonresonant Cavity with Image Bearing Beams","authors":"M. Ingold, M. Duelli, P. Günter, M. Schadt","doi":"10.1364/JOSAB.9.001327","DOIUrl":"https://doi.org/10.1364/JOSAB.9.001327","url":null,"abstract":"A new configuration of an all-optical, nonlinear holographic associative memory [1] is investigated. A multistable, content-addressable cavity is used, that performs image comparison, discrimination and read-out in one step. The required nonlinear processes are obtained by using a combination of a photorefractive KNbO3 crystal and a nematic liquid crystal (NLC) in a feedback configuration with several beams.","PeriodicalId":355924,"journal":{"name":"Photorefractive Materials, Effects, and Devices","volume":"326 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1992-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122739084","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
We have recently demonstrated large two beam coupling gains in lnP:Fe by combining the band-edge resonance technique with a second resonant enhancement involving temperature stabilization.1 While loss increases near the band-edge, the gain increases much more dramatically. Net gain coefficients larger than 20 cm−1 have been measured making semiconductor gains comparable to those in ferroelectric materials. We present here an investigation of this material as a self pumped phase conjugator.
{"title":"Investigation of photorefractive self pumped phase conjugators in the presence of loss and high modulation depth","authors":"J. Millerd, E. Garmire, M. Klein","doi":"10.1364/JOSAB.9.001499","DOIUrl":"https://doi.org/10.1364/JOSAB.9.001499","url":null,"abstract":"We have recently demonstrated large two beam coupling gains in lnP:Fe by combining the band-edge resonance technique with a second resonant enhancement involving temperature stabilization.1 While loss increases near the band-edge, the gain increases much more dramatically. Net gain coefficients larger than 20 cm−1 have been measured making semiconductor gains comparable to those in ferroelectric materials. We present here an investigation of this material as a self pumped phase conjugator.","PeriodicalId":355924,"journal":{"name":"Photorefractive Materials, Effects, and Devices","volume":"20 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1992-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134297344","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
S. Boothroyd, P. Beckwith, L. Chan, J. Chrostowski
Nonlinear optical image subtraction and Boolean XOR operations have been demonstrated in Michelson interferometers with phase conjugate mirrors [1-3], The two interferometer arms each contain a light modulating transmission or reflection element which must be carefully registered and imaged at the interferometer output. Destructive interference between the output images of the two arms arises because one image undergoes a extra π phase change on reflection from a dielectric interface. Image subtraction has also been achieved in photorefractives via double exposure holography [4] where two gratings are formed by displacing the reference beam in phase by π. A π phase shift on one of the writing beams in four wave mixing has also been used to selectively erase volume holograms in photoreffactive media [5-7].
{"title":"Multiple Grating Optical Processing in Barium Titanate","authors":"S. Boothroyd, P. Beckwith, L. Chan, J. Chrostowski","doi":"10.1364/pmed.1991.wc18","DOIUrl":"https://doi.org/10.1364/pmed.1991.wc18","url":null,"abstract":"Nonlinear optical image subtraction and Boolean XOR operations have been demonstrated in Michelson interferometers with phase conjugate mirrors [1-3], The two interferometer arms each contain a light modulating transmission or reflection element which must be carefully registered and imaged at the interferometer output. Destructive interference between the output images of the two arms arises because one image undergoes a extra π phase change on reflection from a dielectric interface. Image subtraction has also been achieved in photorefractives via double exposure holography [4] where two gratings are formed by displacing the reference beam in phase by π. A π phase shift on one of the writing beams in four wave mixing has also been used to selectively erase volume holograms in photoreffactive media [5-7].","PeriodicalId":355924,"journal":{"name":"Photorefractive Materials, Effects, and Devices","volume":"224 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1992-05-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115313386","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In recent years a variety of photorefractive phase conjugators have been demonstrated that rely on stimulated light beams.1-6 These self-pumped and mutually-pumped phase conjugators are all closely related7 and differ only in the number and angle of their input beams. Here we propose a detailed though necessarily simplistic description of how light beams spring up inside a photorefractive crystal, and why under some conditions these stimulated light beams appear to follow curved paths inside the crystal. We show that these curves are composed of a number of straight line segments which spring up by stimulated scattering in the photorefractive crystal.
{"title":"Why Light Beams Follow Curved Paths in Photorefractive Phase Conjugators","authors":"V. Eliseev, A. Zozulya, G. D. Bacher, J. Feinberg","doi":"10.1364/pmed.1991.mc12","DOIUrl":"https://doi.org/10.1364/pmed.1991.mc12","url":null,"abstract":"In recent years a variety of photorefractive phase conjugators have been demonstrated that rely on stimulated light beams.1-6 These self-pumped and mutually-pumped phase conjugators are all closely related7 and differ only in the number and angle of their input beams. Here we propose a detailed though necessarily simplistic description of how light beams spring up inside a photorefractive crystal, and why under some conditions these stimulated light beams appear to follow curved paths inside the crystal. We show that these curves are composed of a number of straight line segments which spring up by stimulated scattering in the photorefractive crystal.","PeriodicalId":355924,"journal":{"name":"Photorefractive Materials, Effects, and Devices","volume":"9 3 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1992-05-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116910900","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Y. Taketomi, J. Ford, H. Sasaki, Jian Ma, Y. Fainman
Holographic memories offer the advantages of high storage density, distributed storage, and fast parallel access. These characteristics can be important for parallel opto-electronic computers such as neural networks. The memory can be used to hold a training set which is repetitively displayed during learning. In addition, if partitioning is used to solve problems requiring more neurons than the actual number of processors, the memory can also be used to hold connection weight and threshold information. In this paper, we present results from a photorefractive memory using incremental recording scheduling and binary orthogonal phase codes image addressing. We show how this approach allows modification of the content and diffraction efficiency of the stored images, and how multiple images can be combined by complex amplitude addition and subtraction during reconstruction.
{"title":"Multi-mode operations of a holographic memory using orthogonal phase codes","authors":"Y. Taketomi, J. Ford, H. Sasaki, Jian Ma, Y. Fainman","doi":"10.1364/pmed.1991.md2","DOIUrl":"https://doi.org/10.1364/pmed.1991.md2","url":null,"abstract":"Holographic memories offer the advantages of high storage density, distributed storage, and fast parallel access. These characteristics can be important for parallel opto-electronic computers such as neural networks. The memory can be used to hold a training set which is repetitively displayed during learning. In addition, if partitioning is used to solve problems requiring more neurons than the actual number of processors, the memory can also be used to hold connection weight and threshold information. In this paper, we present results from a photorefractive memory using incremental recording scheduling and binary orthogonal phase codes image addressing. We show how this approach allows modification of the content and diffraction efficiency of the stored images, and how multiple images can be combined by complex amplitude addition and subtraction during reconstruction.","PeriodicalId":355924,"journal":{"name":"Photorefractive Materials, Effects, and Devices","volume":"22 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1992-05-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123415199","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
J. Khoury, A. M. Biernacki, C. Woods, M. Cronin-Glolmb
A new technique for dealing with multiplicative complex speckle noise on coherently imaged amplitude objects is presented. This technique uses phase cancellation via quadratic nonlinearity to convert the multiplicative noise into additive noise on the Fourier spectrum. This is accomplished using a noisy image as the pump and a clean planar reference beam as the probe in a degenerate four-wave mixing phase conjugator. The counterpropagating pump is provided by the phase conjugate of the noisy image from a total internal reflection self-pumped phase conjugator whose input is the noisy image transmitted through the first crystal. The phase conjugate output is read off from the clean probe; the remaining noise on the Fourier spectrum of the output image is additive and can be removed by nonlinear filtering in the Fourier plane [1].
{"title":"Multiplicative to Additive Speckle Noise Conversion via Phase Cancellation with Photorefractive Phase Conjugators","authors":"J. Khoury, A. M. Biernacki, C. Woods, M. Cronin-Glolmb","doi":"10.1364/pmed.1991.tub4","DOIUrl":"https://doi.org/10.1364/pmed.1991.tub4","url":null,"abstract":"A new technique for dealing with multiplicative complex speckle noise on coherently imaged amplitude objects is presented. This technique uses phase cancellation via quadratic nonlinearity to convert the multiplicative noise into additive noise on the Fourier spectrum. This is accomplished using a noisy image as the pump and a clean planar reference beam as the probe in a degenerate four-wave mixing phase conjugator. The counterpropagating pump is provided by the phase conjugate of the noisy image from a total internal reflection self-pumped phase conjugator whose input is the noisy image transmitted through the first crystal. The phase conjugate output is read off from the clean probe; the remaining noise on the Fourier spectrum of the output image is additive and can be removed by nonlinear filtering in the Fourier plane [1].","PeriodicalId":355924,"journal":{"name":"Photorefractive Materials, Effects, and Devices","volume":"65 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1992-05-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123773193","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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